Method for compression and decompression of a video signal

Abstract

A method for transmitting a sequence of images is provided. The method indes the steps of previously defining that the sequence of images includes a plurality of frame segments and that each of the segments includes two types of images, update frames and intermediate frames, encoding and transmitting the sequence of images and decoding the transmitted sequence of images. When an update frame is present, the step of encoding and transmitting includes the step of compressing and transmitting the update frame. When an intermediate frame is present, the step of encoding and transmitting includes the step of generating and transmitting intermediate global motion parameters describing motion between the update frame and the intermediate frame. When the compressed update frame is received, decoding the transmitted sequence of images includes the step of decompressing the compressed update frame to produce a transmitted update frame. When the intermediate motion parameters are received, decoding the transmitted sequence of images includes the step of warping the transmitted update frame with the intermediate motion parameters thereby to produce a transmitted intermediate frame.

We claim: 
     
       1. A method for transmitting a sequence of images, the method comprising the steps of: a. having previously defined that said sequence of images comprises a plurality of frame segments and that each of said segments comprises two types of images, update frames and intermediate frames;   b. encoding and transmitting said sequence of images, the step of encoding and transmitting comprising the steps of: i. when a update frame is present, compressing and transmitting said update frame;   ii. when an intermediate frame is present, generating and transmitting intermediate global motion parameters describing motion between said update frame and said intermediate frame;     c. decoding said transmitted sequence of images, comprising the steps of: i. when said compressed update frame is received, decompressing said compressed update frame to produce a transmitted update frame;   ii. when said intermediate motion parameters are received, warping said transmitted update frame with said intermediate motion parameters thereby to produce a transmitted intermediate frame.     
     
     
       2. A method according to claim 1 and wherein said step of compressing and transmitting said update frame further comprises the steps of: a. determining the motion of said update frame by warping the previously transmitted update frame with said motion parameters;   b. predicting said update frame from said determined motion information and said update frame   c. calculating the difference between said predicted frame and said update frame; and   d. compressing and transmitting said calculated difference frame.   
     
     
       3. A method according to claim 1 and wherein said step of decompressing said compressed update frame further comprises the steps of: a. warping said previously received update frame with said motion parameters;   b. decompressing said calculated difference frame; and   c. summing said decompressed calculated difference frame with said warped update frame to obtain an estimated update frame.   
     
     
       4. A method for transmitting a sequence of images, the method comprising the steps of: a. having previously defined that said sequence of images comprises a plurality of frame segments and that each of said segments comprises at least one update frame and a plurality of intermediate frames;   b. encoding and transmitting said sequence of images, the step of encoding and transmitting comprising the step of generating and transmitting intermediate motion parameters describing motion between the first of said at least one update frame and said intermediate frame; and   c. decoding said transmitted sequence of images, comprising the step of warping said transmitted first update frame with said intermediate motion parameters thereby to produce a transmitted intermediate frame.   
     
     
       5. A method according to claim 4 and wherein said step of compressing and transmitting said update frame further comprises the steps of: a. determining the motion of said update frame by warping the previously transmitted update frame with said motion parameters;   b. predicting said update frame from said determined motion information and said update frame   c. calculating the difference between said predicted frame and said update frame; and   d. compressing and transmitting said calculated difference frame.   
     
     
       6. A method according to claim 4 and wherein said step of decompressing said compressed update frame further comprises the steps of: a. warping said previously received update frame with said motion parameters;   b. decompressing said calculated difference frame; and   c. summing said decompressed calculated difference frame with said warped update frame to obtain an estimated update frame.   
     
     
       7. A method for decoding a transmitted sequence of encoded images, the method comprising the steps of: a. having previously defined that said encoded sequence of images comprises a plurality of frame segments and that each of said segments comprises two types of images, update frames and intermediate frames;   b. previously selecting from among a low, medium and high delay levels for intermediate frames;   c. receiving motion parameters between update frames and from update frames to intermediate frames and receiving independently compressed update frames;   d. for a low delay level, reconstructing an intermediate frame by concatenating the motion parameters between the previous update frame and the most recent update frame with the motion parameters from the most recent update frame to the intermediate frame and warping the previous update frame with the concatenated motion parameters;   e. for a medium delay level, reconstructing an intermediate frame by warping the most recent update frame with the motion parameters from the most recent update frame to the intermediate frame;   f. for a high delay level, predicting an intermediate frame by i. creating a backward predicted intermediate frame by inverting the motion parameters from the most recent update frame to the next update frame, which came after the intermediate frame of interest, concatenating the inverted motion parameters with the motion parameters from the most recent update frame to the intermediate frame, and warping the next update frame with the concatenated motion parameters;   ii. creating a forward predicted intermediate frame by warping the most recent update frame with the motion parameters from the most recent update frame to the intermediate frame; and   iii. combining the backward and forward predicted intermediate frames into a reconstructed frame     g. decompressing the compressed update frames.   
     
     
       8. A method according to claim 7 and wherein said encoded transmitted sequence of images also includes compressed difference frames and said step of decompressing includes the step of reconstructing said update frames from said compressed difference frames and from motion parameters between first update frames and second update frames.